At present, an upsurge of research on new types of memories rises in the world. There are a great variety of new types of memories. Their mechanisms are different. It is unclear which one can find favor with integrated circuit manufacturers and customers. However, one thing is for sure: in case where performance is assured, to improve the storage density makes the cost of storage of each bit of data lower and its market competence stronger. To a large extent, it determines whether the new type of memory can be used finally. Generally speaking, there are two effective methods that can improve the density of memories. One is to reduce cell area with the aid of processes or design of device structures. For example, a cross-array structure can achieve the theoretical minimum cell area. The other effective measure is to use the multilevel storage unit. It dramatically improves the storage density and reduces the cost of the area per bit without enlargement of the storage area. Its actual application has a preferable market prospect. Currently, various international corporations and research institutes are actively researching on memory technologies based on the cross-array structure and the multilevel storage unit so that they can occupy a leading position in the competitive market in the future.
One time programming memory is very important and widely applied to, for example, storage of permanent materials, storage of codes, calibration tables, setting of parameters, which usually will not be changed once being programmed, because of the advantages of simple structure and low power consumption. The keys of the one time programming memory are low cost, high storage density, low power consumption and quick reading speed. Among the current one time programming storage technologies, the one time programming memory using cross-array can achieve the higher storage density. However, among this kind of one time programming memory technologies using the cross-array integration, the used principle is always to carry out programming in accordance with the state of dielectric (being punctured or not), so such a kind of one time programming memory generally only has two states: “0” and “1”, but it cannot realize multilevel storage.